The whole line was officially closed to passenger trains as part of the Beeching Axe on 18 January 1965. Goods services between Morfa Mawddach (formerly Barmouth Jn) and Llangollen ceased in 1964. Although the whole line was planned to close for passenger services on 18 January 1965, services were suspended on 12 December 1964 following flooding. The section between Ruabon and Llangollen was subsequently reopened on 17 December for passenger trains until 18 January after which only freight services ran until 1968 when the line was closed completely. The section between Llangollen and Bala Junction was abandoned following flooding although a substitute bus service served the stations until 18 January 1965. The section between Bala, Bala Junction and Dolgellau was reopened on 17 December and the section Dolgellau to Morfa Mawddach reopened on 14 December.[6]

A 10 miles (16 km) section between Barmouth Junction and Dolgellau is used as the Mawddach Trail, a cycle route and bridleway, conversion of which was assisted in 1976 when heavy floods washed away most of the remaining ballast. The section between Bala Junction and Corwen remains disused and completely free from redevelopment, currently used as a path in the countryside.

Several sections have been used for road improvement schemes, including a 1.5 miles (2.4 km) section through Dolgellau, and the station site and trackbed west of Drws-y-Nant. The trackbed has also been redeveloped at the west end of Corwen and a number of houses and apartments have been built immediately east of Llangollen. Infringements occur between Llangollen and Acrefair (typically garden extensions and outbuildings) and the cutting through Cefn Mawr is partially blocked following land slips. At the end of Llanuwchllyn station, a house straddles the trackbed.